1. Field of the Invention
The present invention pertains to modification of qualities of a dielectric surface, in particular to render a dielectric surface to be an electric conductor. The invention may be used e.g. in various areas of industry for the preparation of dielectric surfaces of electroplating, especially for nickel-plating. Dielectric items which are metal-coated by processes of the invention may be used e.g. where a decorative or protective function is required, in manufacturing press-forms using the galvanoplastic method, or for assemblies for shielding electromagnetic emission.
2. Background
One existing certain method of producing conductor surfaces is known (USSR patent No 980858, B 05 D 5/12 1982), in which the dielectric surface is treated by amine-salt solution of copper, then immersed in water, then in sulphide solution and then rinsed with water.
Using this method, a quality conductor surface can be obtained by repeating the operation sequence described in the USSR patent at least three times. This increases the duration of the entire process, increases the consumption of water and chemicals and makes the use of automated production lines more difficult.
In addition, another certain existing process for producing conductor surfaces of cupric sulphide is known (USSR patent No 1762454, H 05 K 3/42, 3/18, 1991), in which dielectric items are immersed into solution of univalent cupric salt, then into a solution of 0.0025/0.025 of potassium persulphate, iodine or potassium nitrite solution, then rinsed with water and immersed into sulphide solution of an alkaline metal. This process is carried out at room temperature and each operation is repeated twice.
The shortcomings of the method described in USSR patent No 1762454 are the same as the shortcomings described in the preceding patent. In addition, through application of both existing methods, it is impossible to leave an isolated part of the item uncovered, i.e., it is impossible to achieve selective conductor coating.
See also the patent application of the Republic of Lithuania No 98-161, published in the official bulletin of Lithuanian State Patent Bureau (VPB) No 5 in 2000. That reported method also has notable shortcomiongs, including problematic use of a cobalt solution.
It would be desirable to have new methods to render a dielectric surface electrically conductive.